The proposed work will study the genes involved in synthesis and assembly of the Pseudomonas aeruginosa 1244 pilus, a major surface antigen and virulence factor. These genes will be marked using transposon mutagenesis and will be analyzed as to phenotype. The transposon marker will be cloned from mutants unable to assemble pili and will be analyzed as to physical structure. Minicell studies of these and wild type will be used to identify number, size, relative position, direction of transcription, and polarity of these genes, as well as final subcellular location of the gene product. This information will be used to identify potential antigens for vaccine evaluation.